void getConfig_returnsConfig() {
        SmbTreeConnection c = newConn();
        assertSame(config, c.getConfig());
    }

    @Test
    @DisplayName("acquire calls tree.acquire on first usage, release calls tree.release at zero")
    void acquire_release_lifecycle() {
        SmbTreeConnection c = newConn();
        SmbTreeImpl tree = mock(SmbTreeImpl.class);

     *
     * We start out with a double-precision approximation, which may be higher or lower than the
     * true value. Therefore, we perform at least one Newton iteration to get a guess that's
     * definitely >= floor(sqrt(x)), and then continue the iteration until we reach a fixed point.
     */
    BigInteger sqrt0;
    int log2 = log2(x, FLOOR);